The present invention generally relates to hydraulically arranged continuous filament nonwoven fabrics and methods of making the same.
Nonwoven fabrics are useful for a wide variety of applications, including use as one or more components within personal care products. More specifically, nonwoven fabrics are commonly used within infant care items such as diapers, child care items such as training pants, feminine care items such as sanitary napkins, adult care items such as incontinence products, and personal hygienic care items such as facial and body wipes. Nonwoven fabrics have also found use in garments including protective workwear and medical apparel such as surgical gowns. Other nonwoven medical applications include nonwoven wound dressings and surgical dressings. Cleaning applications utilizing nonwovens include towels and wipes. Still other uses of nonwoven fabrics are well known in the art.
Nonwoven webs of continuous filaments made by melt-spinning thermoplastic polymers are known in the art. Generally described, the process for making spunbond nonwoven fabrics includes extruding a thermoplastic polymeric material through a spinneret and drawing the extruded material into filaments with a stream of high velocity air to form a random web on a collecting surface. Such a method is referred to as meltspinning. Spunbond processes are generally defined in numerous patents including, for example, U.S. Pat. No. 4,340,563 to Appel, et al., and U.S. Pat. No. 3,802,817 to Matsuki, et al.
A particular type of spunbond utilizes multiple polymers in order to make multicomponent or bicomponent nonwoven polymeric fabrics. The term xe2x80x9cmulticomponentxe2x80x9d refers to filaments formed from at least two polymer streams that have been spun together to form one filament, such that the filament has two or more distinct components arranged in distinct zones across the cross-section of the filament which extend along the length of the filament. Multicomponent filaments and methods of making the same are known in the art and, by way of example, are generally described in U.S. Pat. No. 5,382,400 to Pike et al., U.S. Pat. No. 5,989,004 to Cook and U.S. Pat. Nos. 3,423,266 and 3,595,731 both to Davies et al.
The characteristics or physical properties of nonwoven webs are controlled, at least in part, by the density or openness of the fabric. Generally speaking, nonwoven webs made from crimped filaments have a lower density, higher loft and improved resiliency compared to similar spunbond filament nonwoven webs of uncrimped filaments. Such lofty, low density webs exhibit cloth-like textural properties, e.g., softness, drapability and hand. Various methods of crimping melt-spun multicomponent filaments are known in the art. As disclosed in U.S. Pat. Nos. 3,595,731 and 3,423,266 to Davies et al., bicomponent fibers or filaments may be mechanically crimped and the resultant fibers formed into a nonwoven web or, if the appropriate polymers are used, a latent helical crimp produced in bicomponent fibers or filaments may be activated by heat treatment of the formed web. Alternatively, as disclosed in U.S. Pat. No. 5,382,400 to Pike et al., the heat treatment may be used to activate the latent helical crimp in the fibers or filaments before the fibers or filaments have been formed into a nonwoven web.
Nonwoven webs or fabrics used in personal care products, garments, medical applications, and cleaning applications may desirably have apertures or perforations through the web. Apertures are a useful means for fluid management or transport generally, and are particularly useful means for fluid intake and transport with respect to high viscosity fluids.
Apertures in nonwoven webs may be imparted by slitting or cutting through portions of the web followed by stretching of the nonwoven web to pull open apertures at the slits. However, aperturing or perforating by slitting through the web necessarily damages the integrity of the individual continuous filaments. Alternatively, as disclosed in U.S. Pat. No. 4,588,630 to Shimalla, apertures may be formed by heat and compression fusing of the web at discrete sites, followed by stretching of the nonwoven web to pull open apertures at the fused sites. However, aperturing by heat-fusing then stretching has the undesirable effect of leaving apertures the edges of which are defined by hard and potentially abrasive fused thermoplastic polymer, as well as damaging the integrity of the individual filaments.
Hydroentangling has also been used to impart apertures to a nonwoven web. Hydroentangling is a well known principle involving the use of high pressure, needle-fine water jets to cause substantial filament entanglement such that the individual fibers or filaments are intertwined and entangled about one another to a high degree. This high degree of filament entanglement gives functional integrity to the web structure and forms a highly entangled and consolidated fibrous structure. Basic principles of hydroentangling are disclosed in U.S. Pat. Nos. 3,485,706 and 3,494,821 both to Evans. Examples of using hydroentangling processes to effect entanglement bonding and aperturing of webs of staple length fibers are disclosed in U.S. Pat. Nos. 3,747,161 and 4,016,317 both to Kalwaites, U.S. Pat. No. 4,379,799 to Holmes et al., and U.S. Pat. No. 4,735,842 to Buyofsky, et al. In order to impart substantial filament entanglement and give the web structure functional integrity, water pressures from as high as 200 pounds per square inch (psi) to 5,000 psi are described as necessary. However, use of high pressure water in these hydroentangling processes tends to densify or compact the nonwoven web, destroying its loft. Additionally, the mechanical requirements for high pressure hydroentangling such as pumping systems able to operate at high pressures, complex nozzles able to produce high-pressure, needle-fine water jets, and extensive water filtration systems to prevent clogging of the fine jet nozzles are cost prohibitive.
There exists a need for an economically produced apertured nonwoven material retaining high overall loft and, in particular, wherein the loft of the material subjected to an aperturing process is not substantially decreased by the aperturing process. There further exists a need for a high loft apertured nonwoven material wherein the edges of the apertures are unfused, thereby providing a soft fabric with good hand and pleasing tactile aesthetics. Still furthermore, there exists a need for a high loft apertured material having soft aperture edges wherein the integrity of the filaments of the web has not been compromised by a destructive aperturing process.
The aforesaid needs are fulfilled and the problems experienced by those skilled in the art overcome by a nonwoven web made by a process comprising the steps of forming a precursor web of multicomponent substantially continuous filaments, exposing the precursor web to a hydraulic arrangement treatment to form apertures without causing substantial filament entanglement, and thereafter autogenously bonding the web.
In one aspect of the invention, the precursor web comprises a lofty web of crimped multicomponent substantially continuous filaments. In a further aspect of the invention, the precursor web comprises multicomponent substantially continuous filaments which possess latent crimp, which latent crimp is activated after the formation of apertures.